Chan et al. Figure 7. SAR images generated with highlight of the artificial targets. SAR images generated from the scene of Figure 6(a) are shown in Figure 7. First target is spotted at a distance of 1268.10 m from the GBSAR station, whereas the second target can be clearly identified at a distance of 1253.25 m from the GBSAR system. It can be observed that the location of the trihedral coincides with the measurement setup described in the first paragraph of this section. In order to verify the deformation detection capability of the GBSAR system, the tuneable trihedral corner reflector is adjusted by 0.5 mm per step to simulate the changes of the surface deformation. With a different step size of tuning, the corresponding SAR return echo is captured and an SLC image is generated. The phase extracted via interferogram is corrected by taking into consideration the phase errors contributed by atmospheric effect, the predicted phase noise using t-distribution, and mechanical misalign of ground-based SAR system. Figure 8 shows the measurement results obtained via this outdoor field measurement. The y-axis of the graph is the measured displacement based on the phase change of the received signal and x-axis of the graph corresponds to the position of actual displacement of the tuneable trihedral. In this experiment, total of ten steps with each step equivalent to 0.5 mm of the deformation changes have been tested. It can be observed that the developed GBSAR system is capable to perform change detection of 0.5 mm. Figure 9 illustrates the observations of the surface deformation of 0.5 mm via the tuning trihedral. It is clearly shown that the 0.5 mm deformation can be detected via the interferometric phase extracted from the SAR images. With the submillimeter deformation capability, this system is suitable to use for the land deformation study and landslide monitoring in Malaysia. MANMADESTRUCTURALMONITORING The developed GBSAR system can be used for man-made structural health monitoring as well. In this experiment, the radar system was set up to monitor Cingpu Metro Station, Taiwan. The photograph of the metro station with radar setup is shown in Figure 10. The SAR amplitude image generated is overlaid with the Google optical image and shown in Figure 11. Figure 8. Measured displacement versus the actual tune position. Figure 9. Measured displacement of 0.5 mm. OCTOBER 2021 IEEE A&E SYSTEMS MAGAZINE 11